The present invention relates to a process and a device for winding-up textile yarns. In particular, it relates to a process and a device for winding-up continuously delivered yarn, such as winding-up after spinning, at speeds which can attain high values in the range of 6,000 to 7,000 meters/minute and higher.
Wind-up devices or winding machines exist, based on the principle of axial drive. The take-up package is subjected to an axial drive by means of the spindle which supports it. This type of drive allows high torques to be transmitted. However, the control of the peripheral speed of the take-up package, as it increases in size, requires complicated approaches.
Winding machines based on the principle of peripheral drive exist. With these machines, the take-up package is subjected to a peripheral drive by tangential frictional contact with a pilot roller. Rotating at constant speed, the pilot roller controls the peripheral speed of the take-up package in a simple manner and supplies the torque necessary to drive it. However, at high speed, and/or when the torque to be transmitted is high, undesirable slippage between the pilot roller and the take-up package may occur. This slippage results in an irregular take-up speed, variations in tension and heat generation, which leads to a deterioration of the surface filaments.
Winding machines exist which are based on the double drive principle, according to which the take-up package is subjected to a peripheral drive by tangential frictional contact with a pilot roller and to an axial drive by means of the spindle which supports it. The pilot roller, which rotates at constant speed, controls the peripheral speed of the take-up package and can provide part of the torque necessary to drive it, the axial drive providing the remaining torque. A winding machine with axially assisted drive is thus obtained.
For the axial drive, a motor capable of slipping is used such as, for example, a gas turbine. Double drive is advantageous, since it makes it possible for the torque transmitted by the pilot roller to be reduced in the desired proportions and, hence, to avoid the undesirable phenomena of slippage between the pilot roller and the take-up package.
The ratio between the value of the torque supplied by the pilot roller and that of the torque supplied by the axial drive can vary within wide limits according to the circumstances, one of the two values being able to be very small relative to the other. This ratio may be variable during the winding-up process; for example, the value of the torque supplied by the axial drive may be reduced.
In this regard, published Japanese Application Number 49/8,823 describes a winding machine with double drive, namely peripheral and axial drive, with the axial drive supplied by an air turbine, in which the pressure of the air supplied to the turbine is diminished as the take-up package increases in size. The object of this process is to adapt the torque supplied by the turbine to the decrease in the angular speed of the take-up package, in such a way that the turbine always drives the take-up package at the same peripheral speed, which is slightly less than that of the pilot roller. To this end, a pressure regulator is used. In this patent, the diminishing torque from the turbine is retained until the end of the take-up operation.
In many cases, it has been found that slippages occur only at the beginning of formation of the take-up package, and then disappear when the take-up package has attained a certain size.
Indeed, contact between the take-up package and the pilot roller is maintained by means of pressure applied either to the take-up package or to the pilot roller. Due to this pressure, the external surface of the take-up package, which is soft relative to that of the pilot roller, becomes deformed by being crushed and assumes the shape of the pilot roller. The contact between take-up package and pilot roller is not effected along a generatrix, as would be the case for two indeformable rollers, but over an area. At the beginning of the winding-up operation, and as long as the layer of yarn is relatively thin, the take-up package, which is received on a hard support, deforms to a small extent; the contact area is, therefore, small and does not allow the transmission of a high torque without slippage. As the take-up package increases in size, a soft and deformable layer of yarn comes between the hard support and the pilot roller. The deformation of the take-up package in contact with the pilot roller becomes large. The contact area increases until it becomes sufficient to transmit, without slippage, all the torque necessary for the drive. The axial assistance is no longer necessary.